Pipe still



T. O. WILTON -PIPE STILL Dec. 16, 1941.

Filed Aug. 14, 1940 LLI/ 'Pa'tented'Dec. 16,1941

, PIPE STILL Thomas Owston Wilton, Horsham, England Application August 14,

1940, Serial No. 352,591

In Great Britain February 27, 1940 Claims.

This invention relates to distilling plants for tar and the like and it has for its object an improved constructionof pipe stills, and particularly of pipe stills made of cast iron, of large capacity.

By theme of castiron, corrosion in pipe stills has been practically eliminated; the employment of this material, however, has'introduced special problems when units of large size are contemplated, owing to its relatively low crushing strength.

Erosion has also been practically eliminated in pipe stills by using wide sweeping radius return bends; this, however, also introduces special problems when large capacity units are .tobe constructed.

From the result of many years experience in the design, construction and operation of pipe stills for tar distilling, I have evolved a design of pipe still which is characterised by the following features, each of which has been found necessary for obtaining satisfactory results in operation, durability and economy of construction and working:

1. The pipe still is constructed of pipe sections of standard sizes withmachined square flanges which constitute the foundation for the loops which are situated above, the weight of which loops is supported by the flat side of the flanges of the pipe sections immediately underneath, which act as bearing surfaces.

2. The furnace is so disposed that the flames of combustion do not lick the pipe still, which is heated by the hot combustion gases passing round the pipe sections constituting the still and by the radiation of heat by the brickwork of the furnace. By this arrangement, local overheating is prevented and the resulting carbonisation and coking is avoided.

3. The pipe still is built of a number of superposed loops, one above the other, disposed helical fashion, so that the liquid in the piping rises as it travels through the pipe still, so as to permit vapours and gases to travel along with the liquid and to leave the still at the top, instead of accumulating in pockets, where their presence causes carbonisation and burning.

The above three features are now well established practice in pipe still construction, and it is essential that they should be maintained when constructing tar distilling plants of specially large output, necessitating pipe stillsof exceptionally large capacity. Unexpected difficulties have however been met with in the construction of the very large pipe stills demanded by such large plants, the solution of which has ingenuity.

The requirement that the pipe still .shall not be exposed to the flames of the furnace limits the size of the still, for there is an economical limit to the size of the brickwork radiating surfaces: a too great area of'such surfaces would require furnaces of excessive great area, the firing of which would entail a prohibitive fuel consumption. It is found that the greatest radius of bends which it is advisable to use in practice is 3 6". By using semi-circular sections of this size, pipe stills the mean diameter of which is 'I required some feet are constructed, which, when heated by the combustion gases and the brickwork of a central furnace, have a satisfactory performance. This is the limiting practical size for cylindrical pipe stills.

By the combined use of semi-circular sections of this size and of straight pipe sections, oblong pipe 'stills may be constructed on similar principles. In order to avoid an undesirable multiplicity of joints, however, it is not advisable to use more than one pipe section on the straight sides of a pipe still of this-design, and as the greatest length of furnace and of straight pipe section which it is advisable to use for economical working and satisfactory performance is about 9 feet, the size of the pipe still is limited in length also.

' Moreover, it is also limited in the vertical direction, for, owing to the weight of the superimposed material, it is undesirable to increase the number of laps beyond 30, to minimise the risk of fracture of the sections of the lower lap.

It is therefore necessary to increase the size of the pipe still without increasing the size of the bends or of the straight sections connecting these bends, that is, without increasing the overall dimensions of the loops which are coiled to constitute a still, whether in width, length, or height. The use of a single still has also certain advantages, so that it is undesirable to increase the effective length of the still by using two or more coils in series, for this would introduce difficulties in securing even firing and in ensuring a satisfactory circulation of the vapours and gases in the piping of the still.

According to my invention, I provide apipe still of large capacity comprising a single helical coil forming one complete circuit with a uniform rising gradient throughout, constituted by a plurality of partly closed loops in series, each loop partly surrounding a furnace duct of the size ascertained by experience as being thermally the .nique, so as to get the required capacity, the heat being derived from a plurality of furnaces, there being a furnace for each nest of superposed loops,

and said furnaces having-a single furnace flue for Y the e of combustion gases in common, in which is disposed the whole of the coiled groups of loops constituting the pipe still.

Referring to the accompanying drawing, which shows, as an example only, the construction of a pipe still according to my invention:

' Fig. 1 is an elevation in part section;

Fig. 2 is a plan; Fig. 3 is a diagrammatic plan of a pipe layout for a pipe still according to the invention, comprising three nests of superposed loops.

In the figures, I is the outer brickwork, 2 are the furnaces, 3 are the central ducts, I are pipe elements constituting the pipe still, 5 are downtake flues and i are the principal flues leading the combustion gases to the exit 1 to the chimney. Access doors and other usual accessories are provided as may be required.

The combustion gases iss ng from the furnaces heat the brickwork 3 which radiates heat on to the nests of loops of piping partly surrounding them; the gases then pass down the piping and escape by the fiues I, 6 and l.

Hitherto the maximum throughput of a plant built on the principle described above has been about 100 tons of tar distilled per day. With the arrangement according to the invention, it is possible to build plants with a throughput of up to 1,000 tons a day, if desired, without in any way altering the .principle which must be observed in order to achieve safety, thermal economy, satisfactory operation and standard methods of manufacture which have received the sanction ofexperience and alone are conducive to industrial and commercial success.

Such pipe stills would be composed of as many nests of superposed partially closed loops as may be necessary to get the length required, inserted between two end nests of loops similar to the two nests of Fig. 2, as shown in Fig. 3, which represents diagrammatically a unit formed of three nests of loops. In such a unit, the inclination of the piping may be found insufllcient for promoting a satisfactory circulation of the vapours and gases in the piping, unless the lowermost lap be given the required inclination from one end of it to the other, this inclination being followed by the superposed laps, which rest upon it.

What I claim is:

1. A pipe still comprising two separate furnaces disposed side by side, a furnace duct vertically above each said furnace, a furnace fiue surrounding each said furnace duct, the two said furnace fines being adjacent and communicating through i the wall common to both, forming consequently a single common furnace flue for both, furnaces, having the shape of a figure 8, and a pipe coil, having also a figure 8 shape, disposed within the said common furnace flue, with each loop of the figure 8 shaped coil round a furnace duct and close thereto the heating taking place by radiation of the brickwork of the furnace ducts and by the heat of the combustion gases, and the coil being protected by the furnace ducts from direct .contact with the flames.-

2. a pipe still as claimed a claim' 1, m which.

be exactly supe sed, each lap except the top being convex towards the one supporting the weight of the portion of the coil above it, the flanges acting as bearing surfaces for the flanges of the lap immediately above it.

3. A pipe still as claimed in claim 1, in which the top. and bottom of the figure 8 formed by the pipe coil are constituted by straight standard pipe sections identical to each other, there being one straight pipe only in each superposed loop, the sides of the figure 8 being constituted by identical standard semi-circular pipe sections, three in'number, joined so as to reverse the curvature at each joint, the two middle ones inside of the coil, so that each lap has thegreatest possible length for given overall dimensions.

Y 4. A pipe still as claimed in claim 1, in which the lowest lap supports and determines the inclination of the laps of the coil which are above it, and is given such an inclination as to produce a satisfactory circulation of the vapours and gases in the coiled pipe.

5. A pipe still comprising a plurality of furnaces in equidistant alignment, a vertical furnace duct above each furnace, a common furnace flue surrounding said furnace ducts, constrictions in said common furnace flue, at each place between two adjacent furnace ducts, said constrictions being due to two opposite buttress walls advancing from the walls of the furnace flue parallel to the line of furnaces, and a single helical coiled pipe built up of two shapes of pipe sections only, one straight and one semi-circular, consisting of exactly superposed laps, the sides of the laps parallel to the line of furnaces consisting of an odd number of semi-circular sections so disposed as to reverse the curvature at each joint, the end sections being concave towards the inside of the coil, and the ends of the laps consisting of asingle straight pipe section connected at each end to a semi-circular pipe section, with the exception of the inlet and outlet end of the pipe coil, each pair of semi-circular pipe sections concave towards the inside of the coil encircling closely a furnace duct, and each pair of pipe sections circular in shape conve'x to the inside of the coil occupying the constricted space between the said furnace ducts.

6. A pipe still of large capacity built-up with interchangeable pipe sections of two shapes only, identical to those used in the construction of pipe stills of lesser capacity, comprising a single coil each lap of which consists of two straightparallel pipe sections, each end of which, excepting the inlet and outlet to the coil, is connected to the end of a parallel straight pipe section of the adjacent lap by at least three semi-circular pipe bends connected so as to reverse-their radius of curvature at each joint, the outer bends being concave to the inside of the coil, the whole coil being disposed within a furnace flue common-to a plurality of furnace ducts, one said duct being disposed in the space partly enclosed by each pair of semicircular bends having their concavity towards each other, there being constrictions in the furnace flue at the points where two bends have their convexity turned towards each other, and

the pipe sections having square flanges acting as bearing surfaces for the flanges of the pipe sections of the lap immediately above.

"I. A pipe still of large capacity comprising a single coil each lap of which comprises two symmetrical sinusoid-shaped pipes built-up of identical semi-circular pipe sections disposed side by side, two corresponding ends of which are connected by a single straight pipe section, while the other two corresponding ends are connected to single straight pipe sections belonging to the upper and lower next laps, respectively; said straight pipe sections being of such length that the two said sinusoid-shaped pipes are just clear of" each other, a furnace duct in the space left between two opposite semi-circular pipe sections concave to each other, a furnace flue housing said coil, buttress walls inwardly of the walls of said furnace flue in each space left in the concavity of semi-circular pipe sections convex to each other, said buttress walls being opposite each other in pairs, each such pair causing a constriction of the furnace flue, and flanges machined square to said pipe sections, the flanges of one lap acting as bearing surfaces for the flanges of the lap immediately above it.

8. A pipe still of large capacity comprising a single helical coil constituted by a plurality of superposed laps of piping, each lap comprising only two standard flanged straight pipe sections, parallel to each other, each of which is connected to an identical pipe section belonging to the adjacent lap by an odd number of standard flanged semi-circular pipe sections alternately concave and convex to the inside of the coil so as to form at least two nearly closed loops constituting by their super-position in the several laps of the coil at least two elongated stacks connected to each other at each lap by one identical semicircular pipe section convex to the inside of the coil, a furnace below each stack, a furnace duct above each furnace, in the middle of each stack, a furnace flue round each said furnace duct, constituting a housing for the said stack, said furnace flues communicating with each other so as to form one common furnace flue for all the is shaped like a figure furnaces, containing the coil still, the flanges of the pipe sections being square so as to act as bearing plates for the pipe sections immediately above.

9. A pipe still of large capacity constituted by a plurality of superposed laps coiled spiral fashion with a uniform slope gradient, each lap being constituted by a plurality of half loops concave to each other, in series, connected by single identical half loops convex to each other, the half loops forming one side of a lap being connected at one end to the half loops forming the other side of the lap by a single straight pipe section forming the end of the lap, the other two ends being similarly connected to single straight pipe sections forming the opposite ends of the adjacent laps, above and below, respectively, a furnace duct in each one of the oblong spaces between opposite paired half loops concave to each other and an enclosing wall housing the said coil, constituting a furnace flue common to all the furnace ducts.

10. A pipe still of large capacity comprising a single helical coil only, constituted by a plurality of superposed laps built-up of two shapes only of standard pipe sections with square flanges, one straight and one semi-circular, so that each lap 8, the said laps being superposed exactly with the flanges of one lap resting upon the flanges of the lap immediately underneath, the superposed laps forming two adjacent nests of nearly closed loops of piping connected at each lap by a single semi-circular pipe section convex to the inside of the coil, a furnace below each nest, a furnace duct above each furnace, extending vertically along the axis of each said nest approximately up to the top thereof, a furnace flue surrounding each said nest and duct, the two furnace flues communicating so as to form a common flue for both furnace ducts with a constriction between said ducts, said constriction being occupied by the semi-circular pipe sections, convex to each other in pairs, which connect the two nests.

THOMAS OWSTON WILTON. 

